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SUMMARY AND CONCLUSION
Countries around the world are preparing strategies to shift towards the use of renewable energy to meet energy demand, as traditional energy will be depleted one day or another. Solar energy is one of the most abundant renewable energies in Egypt, where the solar radiation intensity ranges between 2000 - 3900 kWh / m2/year from north to south. One of the obstacles using solar energy, it is not available all the time and the intensity of solar radiation varies according to the seasons of the year. Energy storage methods can solve this problem.
Thermochemical energy storage system is one of the thermal energy storage methods. It can be used to store solar energy in the form of heat. The two processes of heat storage and thermal recovered depend on an endothermic and exothermic reverse reaction.
These experiments were consisted of three stages: -
a- The first stage (heat recovery process without incubation eggs)
This stage aims to design chicken egg incubator prototype. Three types of storage materials in active form were used as a heat source inside incubator without incubation eggs. use three materials from thermal chemical storage materials (Silica gel self-indicating - commercial white Silica gel - natural Zeolite) in their active forms as a heat source inside the hatchery prototype for chicken eggs with dimensions (56x39x28.5) cm and a capacity of 25 eggs without incubation eggs. The thermal recovery process was accomplished by designing a system to humidification the storage material to release the heat inside it. The active storage material placed inside a wooden box with dimensions (35x35x5) cm with a capacity of 3.5 kg and passing three perforated tubes of 1 inch (2.54) cm diameter through the material to allow the moist air produced by an ultrasonic humidifier to be carried at air temperature and pressure.
b- The second stage (charging process and energy storage)
This stage aims to design a system to store the solar energy by the thermochemical storage materials, by separating the moisture from the storage materials to be active form again. This stage was implemented using three different methods during August and September of 2019: -
1- Exposing the material to direct sunlight by distributing it on an aluminum sheet of 178 cm long installed in a parabolic solar collector made of a reflective surface of stainless steel with a length of (168) cm and a width (59.9) cm. The surface temperature of the material was measured - the weight of the material before and after the experiment.
2- Storage material (50 g) distributed along an aluminum pipe and installed inside an evacuated tube with dimensions (length 174 - outer diameter 5.8 - inner diameter 4.7 - glass thickness 0.16 cm) installed in a solar parabolic collector. A fan installed in the aluminum tube was used to draw air from the ambient into the pipe, which helps in carrying moisture from the material. The surface temperature of the storage material - the temperature and relative humidity of the outside atmosphere - solar radiation were measured and the weight of the storage material was measured before and after experiment.
3- The storage material was distributed on two shelves (100 g / shelf) inside a wooden box with dimensions (28.5 x 28.5 x 28.5 cm) cm. This box is connected to air has been heated through the passage of an aluminum tube (long 195.5-diameter 3 cm) installed inside the evacuated tube and installed in a solar parabolic collector. The temperature of inlet hot air - the storage material surface temperature at each shelf - the outlet air temperature and relative humidity - the outside air temperature and relative humidity, and the solar radiation intensity were measured, and the weight of the storage material was measured before and after the experiment.
c- The third stage (the thermal recovery process during the incubation process)
This stage aims to use the thermochemical storage material that was chosen (Silica gel self-indicating) as the heat source in the incubator prototype to incubate 25 chicken eggs at the same time with the incubation of 25 eggs inside a traditional (electrically operated) incubator with dimensions (57×66×59) cm. The temperature and humidity were measured in the chamber of incubators – temperature and relative humidity of ambient temperature - Eggshell temperature - Energy consumption and Calculation of hatchability.
The main results can be presented as follow: -
1- The total thermal recovered energy from TCM (QRec, in kWh/Kg) for storage media (Silica gel self-indication, white Silica gel, and natural Zeolite) were 0.165, 0.08, and 0.124 kWh/Kg, respectively.
2- Storage material Silica gel self-indicating is the suitable material for the incubation experiment. It has the bigger total thermal recovered energy (0.165 kWh/Kg) compared with white Silica gel and natural Zeolite. The range of storage material temperature for Silica gel self-indicating was (33.52-37.3◦C) without incubation eggs. So, it is the closest to the incubation temperature (37.5◦C).
3- The minmum and maximum storage capacity of Silica gel self-indicating, white Silica gel and natural zeolite was (0.505, 0.995), (0.28, 0.32), and (0.32, 0.78) kWh/kg, respectively.
4- The efficiency of dehumidification process of Silica gel self-indicating, white Silica gel and natural Zeolite was (56.9,40.1%), (27.1, 29.8%), and(41.3, 21.7%), respectively.
5- The efficiency of thermal recovered process of Silica gel self-indicating, white Silica gel and natural Zeolite was (32.7, 16.6%), (25, 28.6%), and (38.8, 15.9 %), respectively.
6- The average temperature of egg’s location in thermochemical prototype and traditional incubator at incubation period (1-18day) was (35.1-37.6◦C) and (37.9-38.5◦C), respectively and (36.4-37.0 ◦C), (38.0-38.4 ◦C) during hatching period, respectively at average ambient temperature (23.5-29.5 ◦C).
7- The average of relative humidity inside the thermochemical prototype and traditional incubator during the incubation period was (55.7-61.5%) and (57-65.5%), respectively and (61.4-69.4%), (59-62.3%), respectively at hatching period at an ambient relative humidity (37.4-54.4%).
8- The eggshell temperature (EST) during incubation period was measured by thermal camera and results showed that, the variation in EST in prototype and traditional incubator were (36.6◦C at day 3 to 41 ◦C at day 18) and (40.1 ◦C at day3 and 40.7 at day 18), respectively.
9- The percentage of hatchability in thermochemical prototype and traditional incubator were 71.4 and 80.95% , respectively.
10- The total energy consumption (for 21 days) by thermochemical prototype and traditional incubator was 11.2 kWh and 19.25 kWh, respectively. The ratio of energy saving was 41.8%.
This study recommended expanding using the open system of thermochemical materials storage to store solar energy. To improve the thermal storage system, the following point should be taken into consideration:
1- Consider the (availability, cost, and temperature range required for the charging and discharging process) while choosing a thermal storage material.
2- Provide a support heat source in applications sensitive to temperature fluctuations.
3- More research on the proposed prototype of a chicken incubator to improve hatchability and reduce temperature fluctuations.